Tape roll and core



c. B. SAMPAIR 511m.

TAPE ROLL AND GORE Filed Oct. 7,1940

June 6, 1944.

' struction employed therein.

Patented June 6, 1944 Clarence B. Sainpalr and Elbert 0. Land, St. Paul,

Minn, assignors to Minnesota Mining & Manufacturing Company, St. Paul, Minn, a corporation of Delaware Application October '2, 1940, Serial No. 360,056

12 Claims.

This invention relates to an improvement in the artof winding tapes into rolls and to improved rolls of tape, and to the novel core con- To illustrate one of the problems overcome by this invention, reference is made to pressuresensitive adhesive tape having a non-fibrous regenerated cellulose film backing coated wlth a normally tacky adhesive (cf. the United States patent to R. G. Drew, No. 2,177,627, issued October 31, 1939). Such tape is commonly supplied in the form of rolls wherein the tape is wound upon a cardboard core, and a fair amount of tension is used in the winding operation to properly press each turn.in place. A series of tapes are. slit from a web and simultaneously wound into rolls, alternate tapes going to one series of cores mounted upon a common windup bar and intervening tapes to another series of cores mounted upon a second windup bar. It is difllcult to accurately gauge and control the winding tension. In particular, variations may occur as between the difl'erent rolls being wound,

. owing to such causes as an uneven adhesive coating thickness across the width of the web,

uneven drag or friction at the different slitting cuts, and unevennesses of tension resulting from slitting tapes of various diflerent widths from the same web.

As a result certain rolls may be wound with excessive tension. In such rolls the radial compression or squeezing may cause telescoping. This means that a lateral displacement of the turns of the roll occurs toward one side, the

amount increasing outwardly from the core, so

that a funnel-like eflect is produced. This telescoping may take place gradually and the defec tive quality may not be apparent prior to packaging. The present invention provides a way of avoiding the effect, of excessive winding tensions within limits, and of immedately indicating whether the tension has been so great as to warrant rejection of the roll.

A further cause of ultimate telescoping arises from variation in atmospheric conditions. Drying out of the regenerated cellulose film will cause shrinkage. More serious is the efiect of high atmospheric humidities' to which the rolls of tape may be subjected in certain localities of use. Moisture is readily absorbed by the cellulose film, through its exposed edges, and causes swelling, which results in the building up of a considerable radial compression or squeezing. Telescoping results from an attempt to relieve the pressure. Such telescoping in high huinidity 55' atmospheres may result even thoughthe tape was not wound so tightly as to .cause telescoping under ordinary atmospheric conditions.

Much adhesive tape of the kind described is employed in dispensers, in oihces, stores, factories and homes. As telescoping of a tape roll causes an increase in total roll width, the result is that a badly telescoped roll cannot be inserted 'in a dispenser designed for a particular width, while the development of'telescoping after insertion will result in the roll binding against the adjacent side walls so that it will not turn freely. Even if provision is made for this in the dispenser design (which in the case of portable and pocket dispensers or holders would make for unwanted bulk), the transverse displacement of the tape may put it out of desired alignment with other parts of the dispenser to which thetape is drawn.

Furthermore, telescoping creates a bad psychological impression upon the user because of the poor appearance of the roll and he is apt to jump to the unwarranted conclusion that there has been deterioration of the tape itself or that the tape was initially defective.

A further undesirable consequence arising from excessive compressional or squeezing forces, is the tendency to cause'oozing or projection of the adhesive from between the edges of the tape, since the adhesives commonly employed are plastic or deformable. If an adhesive is used which is extremely firm or non-plastic, the adhesive tape may haveother undesirable properties in consequence.

In the accompanying drawing, which illustrates but does not limit the invention:

Figure 1 shows a roll of tape (which may be of the kind hereinafter described) wherein the \tape,is wound upon a special type of core employed to 'overcome'the effects of excessive compressional or squeezing forces set up during the winding of the tape or thereafter;

Fig. 2 is an edge view showing the construction of the cylindrical core upon which'the tape is wound; and i Fig. 3 is an edge view of the same core as it might look after winding and squeezing by'the tape (the tape being omitted from the drawing to facilitate comparison).

This illustrative core is comprised of an inner portion or annulus III, which may be a relatively stifi orrigid cardboard cylinder such as is commonly employed in making rolls of tape. In accordance with this invention, the tape is not wound directly upon this element. Surrounding formingthe. outermost element of core.

; dent from Fig. l, the tape it is wound upon this core, and there is thus provided a cellular and compressible annulus between the tape and the inner annulus of the core:

The inner annulus ll, being relatively still or rigid and non-compressible by the tape, and hence non-contractible, thus provides the same internal base for the roll of tape as in conventional constructions. Its internal radius will not change under squeezing by the tape and hence the rolls of'tape may be readily removed from the windup bar after winding; and may be readily fitted into dispensers or holders designed to receive rolls of a definite core size.

The outer annulus, being compressible and contractible, will yield to compressional or squeezing forces exerted by the wound tape, as is indicated in Fig. 3. Thus the outer radius of the core may be made less and relief provided in this way for the squeezing forces in the wound tape, minimising the tendency of the taperoll to telescope and distort. This outer annulus has a I thickness which is but a small fraction of its inner radius and does not greatly increase the diameter of the tape roll for any given length of tape.

The corrugated or cellular form of construction may be so designed that appreciable compression excessive winding tension has been used,

will not occur until the compressional force exceeds a certain value, which value is in excess of that normally produced in winding the roll with the tape tension not exceeding a specified limit.

In winding a plurality of rolls upon a common windup bar, with tape slit from a web, the insqualities in tension at the different rolls, which might otherwise be excessive as to one or more rolls, is offset by the equalizing action of the cores just described. That is, excessive tension at particular roll sets up acompression upon the-core which causes contraction thereof to relieve the force and results in'a roll of tape which will not telescope;

Should the winding tension be so excessive as to largely crush the outer annulus of the core. re-

' sulting in a tape roll which will telescope, this condition will be apparent at once from the visible condition of the core and the roll maybes et s,sso,soo

caused by unfavorable atmospheric conditions, such as high humidity. which may exist at the place of use, it will be evident that the present core also minimizes this problem. Thus squeezing forces, set up by swelling of regenerated cellulose film tape backings, will cause compression and contraction of the outer portion of the core which will relieve the pressure within the wound tape so that telescoping will either not occur or, in extreme cases, will at least be substantially reduced. F

The same considerations apply to minimization of projection or oozing of adhesive from between the edges of the tape as the result of squeezing of the wound tape.

With certain types of pressure-sensitive adhesive tape, it is desirable to wind the rolls of tape under greater tension than has heretofore been feasible, as for example to minimize the inclusion of air pockets and to cause the adhesive coatin to completely contact the back surface ,of the adjacent film-backing. The present core permits using a higher winding tension without resulting in telescoping: and still higher tensions can be used if desired, with less telescoping than results from the lower tension employed in winding tape upon conventional cores. Thus the range of winding tensions that can be used is widened.

It will be evident that the core need not be constructed as shown in the drawing and hereinbefore described. The corrugations may extend diagonally across the core. instead of being par-- allel to the axis. Other cellular and compressible outer core constructions may be used in place of corrugated paper. l'or'example, the outer annulus may be a strip of sponge rubber or sponge cellulose; or may be formed of a strip of highly creped paper wound on itself to provide the desired thickness.

The invention has been described thus far with particular reference to rolls of pressure-sensitive adhesive tape having regenerated cellulose film as the backing. The advantages 'of the invention, in

whole or in part, will also be obtained in other cases, whether or not the tape is adhesive and whether or not the tape is subject to swelling or shrinking. Thus, use of'the present core will in any case facilitate obtaining uniform results in winding tape into rolls, and will serve as an indicator of excessive winding tensions.

. Mention may also be made of the problem involved in making up mils of strip sheeting where the sheet material is elastic and plastic and it is desired that the widthbe kept within an accurate limit. For example, a tape made of a compound- 5 ed rubber composition used for certain sealing aside as defective. The present core thus auto-- matically indicates a defective condition. v

If a substantial proportion of rolls sho that erator of the slitting and winding machine is immediately warned to change the adjustment so as to reduce the general or average tension. Poor operation of the machine will also pro ptly come which will contract sufficiently (in its outer por- --tion may be taken.

tothe'attention of others so that corrective ac- It will thus be evident that the present invention makes possible a reduction in cost of makpurposes must not exceed a specified widthk when this tape .is wound into rolls, the tension necessarily employed is sufficient to stretch the tape a little, and the tape in the roll tends to retract due to its elasticity. This results in squeezing which ordinarily would cause the tape to spread, owing to its plasticity, and thus increase in width. However, in accordance with the present invention, a core can be provided tion) to relieve the squeezing force, and thus prevent the tape from widening beyond the specifiedv tape rolls, by decreasing the percentage of 7 squeezing or compressional force may vary across defective rolls that are manufactured and, further, that it minimizes the possibility of defec- 'tive rolls going to customers and causing dissatisthe width. This may be due, for example, to non-uniform thickness of the sheet. The present core counteracts this enfect since it will take upexcessive pressures which develop locally, so as to equalize the pressure across the width of the roll.

a,sso,seo

Also the winding of a roll may result in unequal pressures around the circumferenceoi' the core, and these will be equalized.

These desirable results are obtained since the outer portion of the core need not contract uniformly, but may be compressed to different extents in different places. a

What we claim is as follows:

1. As 'a new article of manufacture, a roll of tape wound under tension upon a permanent cylindrical core having a relatively rigid inner portion which maintains a substantially constant internal radius and having an outer portion which is contractible in response to excessive compressionai forces in the tape and serves to indicate whether the tape has been wound with excessive tension, said outer portion having a thickness which is but a small fraction of its inner radius.

2.- As a new article of manufacture, a roll oi tape of a kind subject to the development or squeezing forces, wound upon a permanent cylindrical corehaving an inner annulus which is non-contractible and an outer annulus which is contractible such as to relieve harmful squeezing forces set up in the tape roll and minimize obiectionable distortion of the rolled tape, said outer annulus having a thickness which is but a small fraction of its inner radius.

3. As a new article of manufacture, a roll of tape, of a kind having a tendency to cause telescoping due to swelling of the tape under humid conditions, wound upon a permanent cylindricai core having an inner portion which is noncontractible and maintains a substantially constant internal radius, and an outer portion which iscontractible in response to compression exerted by swelling of the tape so as to reduce the telescoping tendency of the roll, said outer portion having a thickness which is but a small fraction of its inner radius.

4. As a new article of manufacture, a roll of tape, of a kind which has a plastic and tacky adhesive coating upon a strip backing subject to swelling under humid conditions, wound upon a permanent cylindrical core having a non-contractible inner portion of substantially non-varying internal radius and having an outer portion which is contractible in response tocompression exerted by swelling of the tape, so as to relieve compressive forces and minimiz oozing of the tape wound under tension upon a permanent core having a non-contractible inner element and a compressible cellular outer annulus adapted to yield to excessive compressional forces set up in the rolled tape and to indicate whether the tape has been wound with excessive tension, said outer annulus having a thickness which is but a small gated paper whose corrugations extend across the inner annulus and are based thereon, said outer annulus having a thickness which is but a small fraction of its inner radius.

8. As a new article of manufacture, a roll of pressure-sensitive adhesive tape formed of a relatively long and narrow strip of regenerated cellulose film coated on one side with a normally tacky and plastic adhesive, wound upon itself upon a permanent cylindrical core comprised of 1 manent core in making tape rolls, having a reladhesive from between turns of the roll, said outer portion having a thickness which is but a small fraction of its inner radius.

5. As a new article of manufacture, a roll of pressure-sensitive adhesive tape, of the type having a normally tacky adhesive coating upon a film backing capable of absorbing moisture from humid atmospheres and swelling, woufid upon a permanent core having a relatively rigid and noncontractible inner annulus and a compressible and contractible outer annulus adapted to absorb squeezing forces set up in the roll upon ex-' atively stiif and non-contractible inner annulus and a compressible and contractible outer annulus of a nature such that it will be compressed when tape is wound thereon under excessive tension, said outer annulus having-athickness which is but a small fraction of its inner radius.

10. A cylindrical core adapted for use-as a permanent corein making tape rolls, having a relatively stiff and non-contractible inner annulus 1 and a compressible cellular outer annulus adapted to yield to excessivecompressional forces set up in tape wound thereon, said outer annulus hav-' ing athickness which is but a small fraction of its inner radius.

11. A cylindrical core adapted for use as a permanent core in making tap rolls, having a relatively still and non-contractible inner annulus and a yieldable and contractible outer annulus formed of a convolution of corrugated paper whose corrugations extend across the inner annulus and are based thereon. a

5 12. A cylindrical core adapted for use as a permanent core in making tape rolls, having a relatively stir! and non-contractible cardboard inper annulus and an outer annulus formed of a convolution of. corrugated paper whose corrugations extend across the inner annulus and are, united thereto, ailexible 'strip' encircling the 

